I have two TL-PA9020 powerline adapters. On the TP-plc app it shows that they have good conneciton (over 900 Mbps) and if I do an internet speed test it confirms that the connection is at least as fast as my internet connection (130 Mbps).  So why does the red light show in the middle LED on both? They are connected to a network in which all the other powerline adapters are TP-Link AV1200 ones, but I don't think that is the reason, as I just tried to sell them on ebay and the buyer returned them because the red light was coming on and he thought it meant they had a bad connection, and he was connecting them to a network of other TP-Link AV2000 adapters.  They have the most recent firmware (for the UK at least). I know I could just turn the LED off, but that won 't stop them being returned again if I try to sell them.

Grateful for any insights!